On Thu, Jan 12, 2012 at 01:57:11PM -0800, Paul Taysom wrote:> A USB stick with a ext file system on it, would occasionally crash> when the stick was pulled.> > The problem was a timer was being set on the Backing Device Interface,> bdi, after the USB device had been removed and the bdi had been> unregistered. The bdi would then be later reinitialized by zeroing> the timer without removing from the timer from the timer queue.> This would eventually result in a kernel crash (NULL ptr dereference).> > When the bdi is unregistered, the dev field is set to NULL. This> indication is used by bdi_unregister to only unregister the device> once.> > Fix: When the backing device is invalidated, the mapping backing_dev_info> should be redirected to the default_backing_dev_info.> > Created 3 USB sticks with ext2, ext4 and one with both apple and DOS> file systems on it. Inserted and removed USB sticks many times in random> order. With out the bug fix, the kernel would soon crash. With the fix,> it did not. Ran on both stumpy and amd64-generic.> > Signed-off-by: Paul Taysom <taysom@chromium.org>> Cc: Mandeep Baines <msb@chromium.org>> Cc: Greg KH <greg@kroah.com>> Cc: Jens Axboe <axboe@kernel.dk>> Cc: Theodore Tso <tytso@google.com>> Cc: Andrew Morton <akpm@google.com>> Cc: <linux-usb@vger.kernel.org>> Cc: <linux-kernel@vger.kernel.org>> Cc: Alexander Viro <viro@zeniv.linux.org.uk>> Cc: <linux-fsdevel@vger.kernel.org>> Cc: <stable@kernel.org>> ---> fs/block_dev.c | 1 +> 1 files changed, 1 insertions(+), 0 deletions(-)> > diff --git a/fs/block_dev.c b/fs/block_dev.c> index afe74dd..322cd05 100644> --- a/fs/block_dev.c> +++ b/fs/block_dev.c> @@ -110,6 +110,7 @@ void invalidate_bdev(struct block_device *bdev)> * But, for the strange corners, lets be cautious> */> cleancache_flush_inode(mapping);> + mapping->backing_dev_info = &default_backing_dev_info;> }> EXPORT_SYMBOL(invalidate_bdev);

What ever happened to this patch? Is it still needed? Can you stillreproduce the problem on Linus's tree and older kernels?